Spark plug



Patented Aug. 7, 1923.

UNITED PATENT OFFICE WILLIAM s. THOMAS, or LINDEN, NEW JERSEY ASSIGNOB T 'rHoMAs SPARK PLUG COMPANY, or RozELLEPAR-K, NEW JERSEY.

SPARK PLUG.

Application filed November 29, 1920. Serial No. 426,933.

To all whom 2'1 may mow v Be it known that I, YILLIAM h. 'lnonivs; a citizen of the United States, residing at Lindeinin the countv of l nion and State of New Jersey, have invented certain new and useful Improvements in Sparkllugs, of which the following is a specification.

The main ob'ect o f m )resent invention I is to provide improved means for retaining 1o insulated electrodes in the body portions of spark plugs.

Another object is to so constructthe above mentioned means that an efficient seal will be produced and so that the parts will always assume their predetermined positions toinsure proper ignition.

A further object is to make the parts of my invention of asimple and durableconstruction and so that they will not become injured'or impaired while in use or when be ing tightened. i 1

These objects, and other advantageous ends which will be described hereinafter, l attain in the following manner, reference being had to the accompanying drawings in which Figure 1 is anenlarged elevation partly in central section showing a spark plug embodying my present invention, 3 30 Figure 2 is a top plan view of a sealing gasket which forms a part of my presentinvention, i

Figure 3 is a transverse sectional view of said gasket taken on the line 3-43 of Figure 2, and t l 'igure 4; is an enlarged fragmentary elevation partly in section more clearly setting forth the relative position of the parts of my present invention; the jacket of the insulator being shown in outside view.

Referring to the drawings 5 represents a metallic body portion*ha.ving arscrc-w threaded part 6 adapted to be screwed into an internal combustion engine in the usual manner of attaching spark plugs. This body portion has a bore 7 terminating in a ledge. or shoulder 8 to form a seat for a metallic jacket 9 surrounding the insulator it) of an electrode 11. The bore 7 is preferably made cylindrical and is preferably of slightly greater diameter than the cylindrical part 12 of the jacket 9, as clearly shown in Figures 1 and 4. The inner wall of the bod portion 5 above the bore 7 flares upwardly as shown at 13 and the jacket- 9 has an upwardly tapering surface li-opposedto the flare 13 so that there is provided, between the jacket and the inner wall of thebody portion,-an annularl extending space 15. which in vertical cross section tapers downwardly;

The outer surface ofthcjacket9immediately t i above the tapered surface l3npreferably extends ina cylindricalform as shown at lit and the inner surface of the body portion 5 for a short distance immediately above the 1.surface 13 is preferably nade cylindrical as shown at 17 or in other words is concentric to the surface portion 16 of the jacket 9.

Above the surface portion 17 of the body portion 5, the latter is provided with internal screw threads 18 inwhicll' is adapted to lit the externally screw threaded sleeve portion 19 of a gland nut 20.

A metallic sealing gasket 21, as

shown in higures 2 andl'l,

is curved in cross section; preferably being semi-circular in cross sec; tion and having its'upper surface22 fiat. This gasket is adapted tobe positioned so that its curved cross sectional surface enandpositionon the top thercof,a llat washer or gasket 23; said gasket serving to contact with the surface 22 ofthe gasket 21. The

gasket 23 is preferably made of steel and is v adapted to fit in the space between the cvlindric-al surface 1(3-of the jacket and the surface 17 of the bodyportion. The lower end of the sleeve portion '19 of the gland nut 20 is adapted to engage the top surface of the gasket 23 and compress the gasket 21 against the surfaces 13 and liof the jacket and body portionso as to firmly hold the jacket against the seat 8 of the body portion and to keep the bottom end of the electrode 11 in proper spaced relation to the electrode wire 24 which is secured to the body portion 5.

By providing the gasket 21 with a cross: section including a radius or curvature. l have found in actual practice that even though slight irregularities might occur. the pressure of the gland nut against the gasket 21 will cause its curved surface to find its way tocloselv lit in annular relation throughout the entire circumferences of the surfaces 13 and 14 of the jacket and body portion so as to provide a complete seal between the jacket and the body portion. urthermore it is obvious that by providing the above described structure it is impossible to injure or impair the insulator it) even though the gland nut :20 is tightened under great pressure by a thoughtless person since the metal jacket is capable of resisting this action and forms a protection for the insulator which is usually made of porcelain or similar substance. The engagement of the jacket 9 upon the seat 8 limits the downward movement of the jacket so that the sparking points of the electrodes are always kept at their proper distance apart.

The body portion 5 below the shoulder or seat 8 provides a chamber 26 which tapers downwardly and is frusto-conical. The iiisulator 10 below the jacket 9 has a downwardly tapering part 27; the outer surface thereof being concentric with the inner surface of the chamber 26. Thus an annular space is provided by the chamber 26 around the portion 27 ot' the insulator; said space decreasing in area from top to bottom and merging into a lower cylindrical chamber 28 within the body portion as clearly shown in Figure l. I preferably make the chamber 2ti and the part 27 ot the insulator of such relative size that there is a considerable space between the part 27 and the inner wall of the chamber 26. At the same time the thickness of the body portion is made relatively thin to permit quick radiation of the heat occurring from the combustion of gas.

By arranging the chamber 26 and part 27 of the insulator as above described, the noncombusted gases confined in the chamber 26 will, when the exhaust valve of the engine opens and the pressure is sufficiently reduced to permit the combustion of the gases within the chamber 26, expand and pass with great force out of the narrow part of the chamber 26 and this action will thoroughly scavenge the plug body and keep the parts clean. This forcible ejection of the gases takes place owing to the fact that the greater volume of the gas is above the narrowest portion of the chamber and there i a choking of the gases which upon said reduction of pressure causes the complete burning of the gases during the explosion.

While I have described my invention as taking a particular form, it will be understood that the various parts of my invention may be changed without departing from the spirit thereof, and hence I do not limit myself to the precise construction set forth, but consider that I am at liberty to make such changes and alterations as fairly come within the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patentis I. The herein described means for retaining insulated electrodes in the body of spark plugs consisting of a body portion having a bore terminating in a transversely extending seat; a metallic jacket adapted to rest upon the seat, the body portion and the jacket having opposed converging surfaces: an electrode insulator carried by the jacket; a gasket of curved cross section engaging the converging surfaces, and means for ex erting pressure upon the gasket to seal the joint between the body portion and jacket and hold the jacket in position.

2. The herein described means for retaining insulated electrodes in the body of spark plugs consisting of a hotly portion having a bore terminating in a transversely extending seat; a metallic jacket adapted to rest upon the seat, the body portion and the jacket having opposed converging surfaces; an electrode insulator carried by the jacket; a soft metal gasket of curved cross section engaging the converging surfaces; a hard metal gasket seated upon the soft metal gasket. and means for exerting pressure upon the hard metal gasket to force the soft metal gasket into sealing engagement with the body portion and the jacket.

In testimony whereof I have signed my name to this specification in the presence of two subscribing Witnesses.

IVILLIAM S. THOMAS.

Witnesses ELIZABETH GARBE, CHAS. E. Po'r'rs. 

